Internal-combustion engine ignition



w m mm F 7 I 1 M 0 MI E i W u i 4 II. n I 4 M 7% 1 m5 Mflflo. 2 2 M 1-E 1. E5 M a .,.w aw F z 1 me l'rngsl ATTORNEY E. G. LINDER YINTERNAL-COMBUSTION ENGINE IGNITION Filed Jan. 3, 1949 nance of theresonator. In accordance witha further feature of the invention, theresonant circuit may comprise a cavity resonator having a movable tuningelement directly connected to a piston of the chamber. In accordancewith till another feature of the invention, part of the combustionchamber walls are the walls of the cavity resonator, and, moreover, thechamber and resonator walls may be the same. A further feature of theinvention recognizes that there is an optimum sparking frequency for aspark-gap through a gas mixture. Therefore, I provide tuning of thegenerator and tuning and timing of the resonator so that not only doesthe sparking occur in the proper timed relationship, but also at theoptimum frequency to assure an ample firing spark. In accordance withstill a further feature of the invention, the exhaust valve is placed tolower appreciably the cavity resonator Q. Thus sparking when the exhaustvalve is closed, which is the case in most engines during thecompression and firing time of the cycle, is allowed, while sparkingduring the exhaust and intake cycles is efiectively inhibited. Thesparking in one chamber, at a time when sparking is desired in anothercompanion chamber might prevent the desired spark in that companionchamber at the proper time. Further, therefore, in accordance withanother feature of the invention, the opening of a valve may so affectth tuning of the cavity resonator comprising at least a portion of thecombustion chamber that no two combustion chambers can be sparked at thesame time.

Referring now more particularly to Fig. 1, an

internal combustion engine has a cylindrical combustion chamber It withwalls I2, [4, and E8, the latter wall 18 being movable and being thepiston head of the engine. A showing of the ports and valves is omittedfrom the drawing wherever not required for a clear understanding of theinvention. A high-frequency source of electrical energy 20 preferably ofadjustable frequency, as by a dial 22, is coupled by a transmissionline, in this instance shown as a coaxial transmission line 24, to aresonant circuit or resonator, in this instance cavity resonator 26.Cavity resonator 26 includes a movable tuning element, the piston-likewall member 28. Resonator 2B is also coupled to transmission line 36 thecentral conductor 32 of which terminates at the wall l2 connected to theouter conductor 34 of line 30 through wall Hi of combustion chamber lEl.Conductor 32 passes through wall i l through an insulating seal ofdielectric material 36 which closes the chamber IE! against loss ofcompression at the entry of conductor 32. Conductor 32 has, however, agap 3% which is the spark-gap of the ignition system for combustionchamber 10. Pistons l8 and 28 are linked by a mechanical coupling orlinkage 43 which brings both pistons to a predetermined positionrelative to each other on the fillllg stroke of the piston. As willappear more fully hereinafter, the high-frequency source 20 may beactuated by a distributor arrangement which, however, in accordance withthe invention, then serves an entirely different function from that ofthe usual distributor arrangement. On the other hand, the usualdistributor arrangement may be entirely omitted to advantage as willappear more clearly hereinafter.

In operation, high frequency source 20 is excited to supplyhigh-frequency energy to cavity resonator 26. The energy thus suppliedis thereby coupled to line 30 through the cavity resonator 26. Theamount of energy thus coupled to line 38 depends on the tuning ofresonator 26 and is a maximum when the cavity resonator is tuned to thefrequency of the highfrequency source 28. It will be understood thatsource 29 may, if desired, include buffer stages or other isolatingmeans, to prevent the cavity resonator from shifting the frequencythereof to any appreciable degree. The travel of piston 23 may beadjusted so that the cavity resonator is tuned substantially to thefrequency of source 20 at the moment when a spark is desired atspark-gap 38. The amount of energy supplied the resonator 25 is thenadjusted so that sparking is effected when the point of resonance isreached. It will now be appreciated that the source 20 may be adjustedin frequency to provide an adjustment of the time of sparking inrelation to the time of travel of piston [8 of chamber Iii, so thatadjustment by means of adjusting the relative movements of the piston l8and piston-like member 28 may be dispensed with. The Q of cavityresonators such as resonator 26 may be made exceedingly high, say of theorder of 10 to 20 thousand. The frequency to which the resonator istuned is thus sharply and definitely dependent on the position of tuningmember 28. Hence the point of travel of tuning member 28 at which thespark will jump across spark-gap 38 may be determined with greatdefinitude and sharpness with respect to the position of piston l8.

A further refinement of th invention may be effected by causing chamber10 itself to become electromagnetically resonant at the desiredfrequency at the desired point of its travel for sparking. The fieldstrength built up to break down the spark-gap 38 across the terminals ofconductor 32 defining th spark-gap is thereby increased at resonance.This may be accomplished, for example, by suitably relating the sizes ofcavity resonator 26 and chamber H] to be of the same size if they areexcited in the same mode of oscillation. It will be understood by thoseskilled in the art that the modes of oscillation chosen are preferablythose which minimize currents between the fixed and movable walls of thecavity resonator or resonators to avoid the lowering of the Q and therequirement of good electrical contact at high frequencies between thewalls movable with respect to each other. The cavity resonator walls maybe of high conductivity,'for example, silverplated. The arrangement ofFig. 1, just described, having a separate cavity resonator hastheadvantage that carbon and other extraneous material does notdeleteriously affect the high Q of this separate resonator. However,this arrangement does require a separate mechanical linkage.

Referring now more particularly to Fig. 2, a cavity resonator 50 iscoupled to the oscillator 28 through transmission line 24 sealed intothe engine wall I l shown enlarged to make room for the cavityresonator. The cavity resonator 5B is coupled to the combustion chamberIn by transmission line 30 which passes through wall M in this case. Thecentral conductor 32 of line 39 may be supported by means well knownwhich may provide free communication for gases between cavity resonator50 and chamber I0. Thus differential pressures are avoided. However,such free communication may be prevented if access of gases to resonator50 may adversely effect wall conductivity. A central cylindrical saga;

projection llf tem piston l Bbifits. 'thefwaills" of cavity resonator 50the cavity of whichIis hollowed Tout wan "I 4. Projection .52 may formonly a loosefit withthe side wallsojlthelhollowed portion if the mode ofoscillation is properly chosen, for example, to be the TEou mode 'having.circular electric lines of force and excel tionallyhigh Q'. Thus thedirect electrica'l contact of projection 52 with the ,-side-walls orcavity resonator 50. becomes unimportant. The coupling of transmissionline 34 to cavity resonator Ellis byaprobe 54.

Thearrangement of Fig,'2-operates in-amanner similarto that-of Fig. 1..Source ZlImayQ-be tuned to determine the point'of travellofprojection=52-at which the .sparkgap :38 fires, aswillbe clear'to thoseskilled inthe-art ofr-electronicsand cavity resonator-s. Further, thedimensions of cavity resonator 50 maybe chosen toproviderthe desiredresonance at the desired-point of travel at'a frequencyto conform to theoptimum sparking frequency for thegaseouscombustionmixture in chamberIll. That there are such. optimum frequencies is evidenced by thearticle by Herlin and Brown in the Physical Review, vol. 74, page 2391'(1948), and one appropriate to a reasonably dimensioned cavity resonator50 may readily be chosen, as a generalrule. The arrangement of Fig.2 hasthe advantage that no separate 'gearing or mechanical linkages arerequired, since the tuning member of cavity resonator 50, in thisinstance the projection 52, is directly connected mechanically to the.movable wall member of combustion chamber l'll that is, to-theypistonl8.

Referring now to Fig. 3, which is a cross-sectional view of anembodiment of the invention similar insome respects to thatof'Fig. 2,the'cavity resonator 50 is not coupled through a-separate transmissionline to oombustionchamber. it, but .i's-itself an auxiliary combustionchamber. Cavityresonator 50 is preferablyexcited in the dominant .TM'mode, in which eventa strongelectric field is created between the,central portions 56 'and 58 of the circular end walls respectivelyof the.cylindrically shaped resonator. Central' portions 56; and 58 thenbecome the terminalsof a spark-gap which is the space between them.These terminals andthe:spark-gapbetween them are obviously in circuitwith the cavity resonator -50-,-being a part of ithewalls thereof. Inthisembodiment -I prefer to add pointed metallic projections '6'4 and 66 which approach in .near contact witheach other at the time forsparking and which extend from central portions 56 and.58. Theprojections 56 and 58 :are then the terminals between which is the:spark-Igap. flhese projections 56 andfifi tend to increase the:fleldigradient 'in the spark-gap between them .and 'thereby'aid abreak-down of the gas 'at resonance. Cavityres onator 50 and combustionchamber-Hircommunicate with each other freely, if not at the moment offiring, then shortly thereafter; injthe, engine cycle, depending on thedesign and-modeof-excitation .of cavityxresonator 50, the;compressionratios desired, and the; degree of electrical contact required betweenprojection 52 and the side walls of cavity, resonatoriflv Thuscombustionoccurs :in both chambers. Therefore, a portion of combustion chamberIll] is identical -with cavity resonator. .58. Projection 52 may be"considered aipart-of the piston 48. Time of spa-rkingiinfrelation; topiston position again may be controlled by controlling-thefrequency ofsource 20. v I

Referring now more particularly to; Fig. :4, which is a cross-sectionalview of an embodiment of .tlie inventiondnwhich cavity resonatortai andcombustion chamber -l I] have-identical walls. onaXial transmissionline"24 is coupled to thecavi'ty resonatorby a coupling loop 'lll. Thecentralcondoctor. is .passed through dielectric I sealing material "12.T11 .sufiic'ien'tly high frequencies are used, the central conductor maybe omitted, the outer conductor of transmission line .24 having suitabledimensions to act as .a waveguide'transmission line andappropriatecoupling means then being; substituted for coupling loop T0 and-the diselectric sealing material sealing .the aperturelin Wall 12 leading tothe waveguide. "There is a spark gap l4;between the point of a-sc'rew1-6 in wall! of chamber), and the central .portion of cylinder 13'. Thispermits adjustment of the gap with a .certain amount of tuning of thecat ity resonator. Timebf sparking may be controlled, as before, byadjustment of the frequency of source 20. Moreover, inamulti-cylinderengine, allcombustion chambers may be resonated byadjustment of screw 16at the-corresponding positions of piston t8, after which the timing ofthe sparking may beeffected by frequency contro1dial22 for theengine asa whole. This result may be reached wherever the cavity resonator may betuned separately from the moving tuning member.

Referring now more particularly to Figs. 15, 6 and '7 whicharerespectively a cross-sectional view of still another embodiment of theinvention and partial cross-sectional views thereof, combustion chamber]0 is again identical with cavity resonator 68. The construction andoperation is similar to the arrangement of 4, except that there is noscrew 16. Instead, a capacitive projection 86 is attached to the walll'd of chamber In. From capacitive projection 80; which may becylindrical as shown, there is a pointed metallic probe 82' projectingcentrally thereof which tends to increase the gradient of theelectric-field inthe vicinity of thepoint and across the sparkgap'84 (asseen in 'Fig. 7") of which probe'82 is one terminal. The other terminalof spark-gap '84 is. a metallic "wire-like loop -86. Loop 86 is arrangedin such a manner that 'in' the sparking position of the ,parts asillustrated bythe partial cross sectional view of Figs;6 and 7, theprobe 8'2 and loop 86. are substantially'spaced equaldistances from'eachother throughout the time of travel of piston 1'8 durin'gwhichthecavity res onator 6E (identical with combustion chamber 1:0)approaches,:and'recedes with the travel 01' piston ['8 from"itsfcondition of resonance. The purpose of thecapacitive projection-.88which'is incapaciti-ve relationship particularly with piston I8 is tocause the capacity between the "end walls OfiCSzVltY resonator 68tochange withg-reat- -er rapidity with the motion 'of piston l8- thanwould be :the case were the projection 89 absent. Therefore, thefrequency of resonance changes with greater rrapidity with motionof-piston l8, and consequently the position of the piston at whichsparking occurs across spark-gap 84 fora definite frequency of source 20is defined with greater accuracy. The arrangement of probe 82 and wire864s such that the spark-gapbetween these terminals is of a fixeddistance throughout the rangeof motion of piston 18 within whichanyafaotor which might include the spacing of the terminals acrossspark-gap's l.

Referring now more particularly to Fig. 8, which is a cross-sectionalview of an embodiment of the invention. Combustion chamber I and thecavity of cavity resonator 68 occupy the same space. A plate I00, havingconsiderable capacity with piston I8, is adjustable by a screw H12.Screw It, with a pointed probe end, similar to screw 16 of Fig. 4 butdifferently placed, is also threaded through wall [4. The probe may beadjusted for a desired spark-gap spacing and serves as one terminaldefining the spark-gap and being coupled to cavity resonator 68 throughthe. walls thereof. The other terminal of the spark-gap is a portion ofthe cavity resonator wall formed by piston l8. Capacitive plate 100 maybe adjusted to give sparking at a desired frequency, the probe beingadjusted for a desired spark-gap length. The probe increases the fieldgradient across the spark-gap. The position of the probe screw 16 isdetermined largely by the field configuration of the mode of excitationof cavity resonator (i8. As understood by those skilled in the cavityresonator art, there may well be more than one preferred position amongwhich a choice may be made as desired. For a different adjustment ofprobe 16, a different adjustment of plate N39 is required to resonatecavity resonator 68 at a desired frequency. The operation of the deviceand the advantage of plate I00 as a capacitive projection from wall i4will be understood from what has been said heretofore. Source 2i! may beadjusted in frequency to cause sparking at a desired point in the enginecycle.

Thus far, no particular comment has been made upon the part which adistributor system may or may not play in the practice of the invention.As the invention relies upon the tuning of a resonator for causing aspark across the spark-gap at the desired instant of time, it is clearthat a distributor in the ordinary sense is not required. However, adistributor may be used, if so desired, particularly in multi-cylinderfour-cycle engines, to provide energy to a particular combustion chamberof such an engine only during an interval of time which startsimmediately before and ends after the time at which sparking is tooccur. In prior systems, sparking energy is applied at the precise timeor instant that firing of the spark gap is desired. However, in thesystem of the invention, energy is applied by means of a permanentconnection such as coaxial line 24 of Fig. 1 or by means of a suitabledistributor continuously from before to the time at which the motion ofthe tuning element tunes the resonant circuit such as chamber 26 of Fig.l to the frequency of the applied energy. Such an arrangement as one ofthose proposed herein does not rely on the distributor for the time ofsparking in relation to the firing cycle except in a secondary sense.Such a distributor system may be desirable, however, in order to preventa nonfiring combustion chamber the piston of which reaches the samerelative position at the same time as the piston of a firing chamber,from sparking and its being fired at the same time as the chamber whichis at the beginning of its firing stroke. However, I can dispense evenwith such a distributor. For this purpose a port of the engine which isclosed at the time sparking is desired and open at the correspondingpiston position when sparking is not desired and suitably to affect theQ of the cavity resonator when open. Referring now more particularly toFig. 9, which ,is a cross-sectional view of such an arrangement similarin most respects to that of Fig. 5, and bearing similar referencenumerals, there is a port in wall M which may be the exhaust port ofcombustion chamber I0. Valve head 92 serves as a closure for exhaustport 90. The entry of exhaust port 90 into combustion chamber In(identical with cavity resonator 68) is located, having due regard tothe mode of excitation of cavity resonator 68, so that when the valve 92is open, the opening of port 90 in the cavity resonator 68 causes the Qof cavity resonator 68 to be appreciably decreased. The appropriateposition in a wall of resonator 68 for particular modes of excitationwill be well understood by those skilled in the cavity resonator art.The position of the port is preferably chosen to interrupt the heaviestcurrent fiow in the resonator walls consistent with the requirements forits other function in exhausting gases. Consequently, when the valvehead 92 is in the open position, the Q of cavity resonator 68 is lowcompared to the Q of the cavity resonator when valve head 92 is in theclosed position and serving as a closure for combustion chamber H! atthe end of the compression stroke of piston l8 and just at the time whensparking is to occur across gap 8 5. It will now be apparent that if anengine includes a plurality of combustion chambers such as combustionchamber Hi, all being similar, that on the termination of the exhauststroke of one of the chambers It, the piston l8 and valve head 92 willbe in somewhat the position as shown in Fig. 9, with the exhaust port 96open and the Q of cavity resonator 68 decreased. Another piston l3 willthen be in a similar position and the parts of combustion chamber iswill be similarly located except that valve head 92 will be in a closedposition, if the engine is of the customary four-cycle multi-pistontype. The combustion chamber is having valve head 92 closed, however,will have a comparatively high Q and accordingly the energy from source29 which may be coupled simultaneously to all the cavity resonators 68(and chamber [0) of the multicylinder engine, will cause a spark only inthe spark-gap il of the high Q chamber, assuming that the spark-gaps areappropriately adjusted. The transmission line it in such an arrangementmay be appropriately branched with a branch 94, for example, to lead toother combustion chambers, only one such branch being shown in Figure 8.It is not harmful, and may be helpful, if the firing chamber is firedtwice, once by a spark at the usual time a few degrees before the pistonreaches the top of its travel, and again as it is making the powerstroke, when it again passes the critical position of resonance.However, it does not fire on the exhaust stroke when the exhaust port isopen.

It will be noted that in addition to decreasing the Q of the cavityresonator 68, valve head 92 acts also as a capacitive projection which,at the time the port is open, tunes the resonator to a differentfrequency. In consequence, the detuning may be made sufficiently great,as by an added projection on the valve head 92, that the sparking inchamber 68 across spark-gap 84 occurs at a different time from thesparking with the port 90 closed. Thus the companion chamber is notfired at the same time. If, for example, a companion chamber timed toexhaust when piston l8 was making its compression stroke (andvice-versa) were sparked when chamber 68 was 11 combustion chamber andthe cavity of said cavity resonator occupying the same space.

18. The combination claimed in claim 9, said movable wall member andsaid tuning element being the same member.

19. The combination claimed in claim 18, said movable wall member beinga piston and said cavity resonator having one of the cavity wallsthereof defined by said piston.

20. In combination with an internal combustion engine having acombustion chamber with a movable Wall member, a high frequency circuithaving a spark-gap in said chamber and comprising a cavity resonatorhaving a tuning element movable in timed relation with the said enginemember, means to apply high frequency energy to said circuit from asource of high frequency energy, continuously from before to the time atwhich the motion of said element tunes said chamber to the operatingfrequency of said source, whereby the precise time of firing of saidspark-gap is determined by the position of said element, said chamberhaving a wall with a port therein closable by a closure, said wall withsaid port being also a Wall of said cavity resonator, said port beingopened and closed by said closure in timed relation with said movablewall member and being positioned to decrease the Q of said chamber withthe port open over the Q of said chamber with the port closed by saidclosure.

21. The combination claimed in claim 20, said movable wall member beinga piston.

22. The combination claimed in claim 20, said port being an exhaust portfor said engine.

23. The combination claimed in claim 20, said engine being a four-cycleengine, said port being an exhaust port.

24. In combination with an internal combustion engine having acombustion chamber with a, movable wall member, a high frequency circuithaving a spark-gap in said chamber and comprising a cavity resonatorhaving a tuning element movable in timed relation with the said enginemember, means to apply high frequency energy to said circuit from asource of high frequency energy, continuously from before to the time atwhich the motion of said element tunes said chamber to the operatingfrequency of said source, whereby the precise time of firing of saidspark-gap is determined by the position of said element, said chamberhaving a wall with a port therein closable by a closure, said wall withsaid port being also a wall of said cavity resonator, said port beingopened and closed by said closure in timed relation with saidmovable'wall member and being positioned to alter by its motion betweenopen and closed positions the frequency of resonance of said resonator.

25. The combination claimed in claim 24, said closure being a valve headand having a capacitive projection to increase the frequency alterationover the alteration that would be effected without said projection.

26. The combination claimed in claim 24, said closure being a. valvehead, said movable wall member being a piston.

27. In combination with an internal combustion engine having acombustion chamber with a piston, a high-frequency circuit having aspark-gap in said chamber and comprising a cavity resonator the cavityof which occupies at least a portion of said chamber, said cavityresonator having a tuning element comprising s i 12 piston and the wallsthereof having a projection in a position toward which and away fromwhich said piston travels and said projection having a highly capacitiverelation to said piston means to apply high frequency energy to saidcircuit from a source of high frequency energy, continuously from beforeto the time at which the motion of said element tunes said chamber tothe operating frequency of said source, whereby the precise time offiring of said spark-gap is determined by the position of said element.

28. The combination claimed in claim 2'7, Said spark-gap being definedbetween terminals at least one of which is a pointed probe. W

29. The combination claimed in claim 27, the position of said projectionbeing adjustable whereby resonance of said cavity resonator and sparkingacross said spark-gap may occur at an optimum frequency with regard tothe gas in said chamber.

30. In combination with an internal combustion engine having acombustion chamber with a piston, a high frequency circuit having aspark-gap in said chamber defined by terminals at least one of which isa pointed probe and comprising a cavity resonator the cavity of whichoccupies at least part of the space of said chamber, said cavityresonator having a projection in a position from which and toward whichsaid piston travels and said projection having a highly capacitiverelation to said piston, said probe extending from said projection, saidpiston being a tuning element for said cavity resonator means to applyhigh frequency energy to said circuit from a source of high frequencyenergy, continuously from before to the time at which the motion of saidelement tunes said chamber to the operating frequency of said source,whereby the precise time of firing of said spark-gap is determined bythe position of said element.

31. In combination with an internal combustion engine having a pluralityof combustion chambers each with wall member movable in predeterminedtime relation to the others, a high-frequency circuit having a spark-gapin each of said chambers and comprising a plurality of resonators onefor each chamber and each resonator having a tuning element movable intimed relation with said movable wall members, and a source ofhigh-frequency energy coupled to each said resonator means to apply highfrequency energy to said circuit from a source of high frequency energy,continuously from before to the time at which the motion of said elementtunes said chamber to the operating frequency of said source, wherebythe precise time of firing of said spark-gap is determined by theposition of said element.

32. The combination claimed in claim 31, said resonators each being acavity resonator having walls identical with the walls of said chambers.

33. The combination claimed in clam 32, the frequency of the energy ofsaid source being adjustable.

34. The method of producing a spark in the combustion chamber of aninternal combustion engine with a movable Wall member and having aresonant circuit coupled to terminals defining a spark-gap in thecombustion chamber, comprising the steps generating high-frequencyenergy of a predetermined frequency, applying said energy to saidresonant circuit, and thereafter and during application of said energytuning the resonant circuit in timed relation with said a e mem er f omnon-resonance to reson- 13 ance at said predetermined frequency, tocouple said resonating energy to said terminals with, suflicient energyto produce a spark across the spark-gap at a time determined preciselyby the moment of tuning said resonant circuit to said i resonance.

with respect to the movable member.

ERNEST G. LINDER.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number 14 UNITED STATES PATENTS Name Date Anderson Dec. 27, 1921 JuneMay 21, 1935 Lindenblad June;.4, 1946 Eitel June 25-, 1946 Mercer Oct.29, 1946 Carter Mar. 18,1947 McIlvaine Feb. 8, 1949

